Pulse Code Modulation (PCM) is commonly used for communications. For example, much of the telephone data (voice, video) that is transmitted digitally is transmitted with the data in PCM format over T1 telephone lines.
PCM data is generated by sampling the amplitude of an analog signal and then digitally encoding the sample signal. When PCM data is transmitted over a telephone line, each data word is converted from 13 into 8 bits using nonlinear compression techniques. Two widely used conversion standards are .mu.-Law (for North America and Japan) and A-Law (for the rest of the world). A-Law and .mu.-Law conversion compress the data logarithmically, wherein low and normal volume levels of the signal are sampled with greater amplitude resolution than are high volume levels. Once the PCM data is generated and compressed, it can readily be sent over T1 telephone lines (or E1 TDM lines).
Computer systems are often connected to T1 telephone lines in order to communicate with other systems. For example, Digitized Analog Data can be sent in PCM form over T1 lines from one computer system to another computer system. The computer system processes the data in a decompressed or linear form. Thus, when PCM data is to be transmitted by one computer system, the data must be compressed to 8-bit words. When PCM data is received from a T1 line, it must be decompressed (for example, from 8 bits to 16 bits) in order to be usable by the receiving computer system.
Some applications, such as video conferencing, require real time data processing of the PCM data sent over telephone lines. One technique used to speed processing is to provide multiple processors in a computer system, wherein each processor can process a portion of the data. However, the compression or decompression process introduces some delay and processing overhead into prior art systems. As well as the need for dedicated look-up tables in memory.